Aviational spraying

ABSTRACT

A method of aerial spraying of crops by airplanes mounted with spray jets below and trailing the wings is disclosed. The method comprises the steps of directing the spray jets at an acute angle with respect to the lower plane of the wing against a winglet deflection surface of covex shape. The winglet extends at a level distanced from the jet and tilted by an accute tangential angle with respect to the plane of the wing. An airplane mounted with a device for effecting crop spraying according to the method is disclosed as well.

BACKGROUND OF THE INVENTION

The present invention relates to the art of aviational spraying ofagricultural crops.

Spraying of agricultural crops by airplanes is traditionally known andis performed by a light airplane flying low over a field and releasingtherebehind a "vapour trail" of fine droplets of a chemical preparationsuch as insecticide. The spraying is effected by a series of especiallydesigned spraying jets, the jets being mounted to and in communicationwith an elongated spray boom, carrying the chemical preparation inliquid form. The boom extends alongside and somewhat lower than thetrailing edge of both airplane wings.

It has been already recognized that the conventional method of airbornespraying--despite its obvious advantages--is in some respects lesseffective than the manual or vehicular, on-site spraying methods,whereby the chemical preparations are directly applied to the desiredlocation around the stems of the crop.

Thus, in aviational spraying considerable proportions of the totalquantity of chemical preparation sprayed in the vapour trail are oftenblown off target, i.e. away from the area to be sprayed, by prevailingbreezes, the occurrence of which not only results in a waste of costlymaterials and time, but also has a negative ecological impact on and maydamage neighboring fields, particularly in cases where herbicides aresprayed.

Secondly, since the droplets descend by gravity only, a significantamount thereof merely rests on the leaves or the boughs of the plants,rather than penetrates down to the ground, near the crop stems asrequired for insecticidal or other effects.

SUMMARY OF INVENTION

It is therefore the general object of the invention to provide a methodof aviational spraying of agricultural crops in the form of a vapourtrail of droplets, that will increase the percentage of dropletspenetrating crop foliage to settle in the desired location on the groundaround the crop stems.

It is a further object of the invention to afford a transporting airstream for the sprayed vapour trail of droplets, having a downwardlydirected inverted vortical path--similar to a whirlwind--thereby causinga higher proportion of the droplets to penetrate within the foliagecanopy and possibly also to settle on the bottom, face-down sides of thecrop leaves--a matter of great importance for treating certain kinds ofplant diseases.

It is a still further object of the invention to reduce the quantity ofchemical preparation required for the airborne spraying of a given area.

It is yet a further object of the invention to provide an aviationalcrop-spraying method being less dependent on prevailing weatherconditions so that it may therefore be more safely applied.

Extensive experimentation by the applicants has proven that the mosteffective way of attaining these goals involves the use of a deflectionsurface, or winglet, affixed at a distance from the spray nozzle jets,so that the mist of droplets becomes deflected by the turbulence(Venturi effect) of the trailing airstream passing over, below andthrough the winglet (see below), thus transforming the ordinarilystraight descent by gravity of the vapour trail into a whirling,inverted vortical path of progressively increasing radii as the dropletsapproach ground level.

It is thus provided according to the present invention a method ofaviational spraying of crops by airplanes with spray jets providedbehind and below the airplane wings, comprising the steps of directingthe spray jets at an angle of preferably between 60-75 degrees withrespect to the lower wing plane, against a winglet comprising a convexdeflection surface having a radius of curvature of preferably between20-40 cm., extending at a level distanced from the jet and tilted by atangential angle of 15-30 degrees with respect to the said wing plane.

The width of the deflection surface is preferably between 30-100 cm, aplurality of such surfaces being provided underneath a series ofalligned spray jets.

Still more advantageously, the said deflection surface constitutes thetop wall of a convergent tunnel comprising a bottom wall conforming tothe shape of and extending distantly from the top wall, and twoopposite, planar side walls, so that rectangular inlet and outletopenings are defined.

The cross-sectional area of the inlet opening should preferably be abouttwice the cross-sectional area of the outlet opening.

For attaining a better understanding of the present invention, referenceshall be made to the accompanying drawings, illustrating a preferredapplication and embodiment thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view of an airplane provided with deflectorwinglets according to the invention;

FIG. 2 is a top view of the airplane of FIG. 1;

FIG. 3 is a side view of the airplane of FIG. 1;

FIG. 4 is a side view of a spraying jet with its associated wiglet;

FIG. 5 is a view taken along line V--V of FIG. 4;

FIG. 6 illustrates the location and allignment of the spray jet andassociated winglet with respect to the airplane wing;

FIG. 7 diagrammatically illustrates the vapour trail extending in thewake of a winglet and the spiralling vortical path by virtue of whichthe droplets penetrate through crop foliage;

FIG. 8 shows the airplane of FIG. 7 from the rear; and

FIG. 9 is an enlarged schematical view of the droplets path penetratingthrough the foliage canopy down to the ground.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIGS. 1-3, a spraying airplane 10, having a pair of wings 12and a conventionally installed spray boom 14 with associated spray jets(or nozzles not shown), is provided with a plurality of winglets 16deployed along the boom 14 in a manner and according to the designconsiderations as will be described in more detail below.

Hence, as seen in more detail in FIGS. 4 and 5, the plane boom 14carries the liquid chemical preparation to a plurality of spray jets,generally denoted 18, of conventional design and therefore not describedin greater detail.

Although the effect, forming the ultimate object of the invention, ismost advantageously achieved using a hollow, double-wall, convergent,duct-like winglet 16 as shown in FIG. 4 and described below--it shouldbe noted that essentially, it may also be attained by providing only asingle deflection surface, namely a convex flap 20 extending underneaththe orifice of the jet 18 normal to the spraying direction thereof.

Thus, the winglet 16 consists of a curved duct, made of sheet metal,comprising the upper wall 20, a lower wall 22 and two planar side walls24 and 26. A pair of ears 28 (only one appearing in the FIGS.) are fixedto the side walls, connected to a bracket 30 by a rivet or bolt 32. Thebracket 30 is T-shaped, whereby its two arms 30a and 30b are used totighten the winglet 16 to the boom 14, e.g. by a pair of standardtraction bands 34, as shown. Any other suitable mounting method is, ofcourse, applicable.

It has been found that the following relative distances, inclinationsand dimensions of the winglet and nozzle with respect to each other andto the wing of the airplane should be kept for attaining best results(see also FIG. 6): The radius of curvatures R1 of the wall 20 is about10% greater than the radius R2 of the wall 22, both being in the rangeof 20-40 cm.; the cross-sectional area A1 of the inlet opening is abouttwice the area A2; the width of the winglet is about 70 cm.; thedistance L between the outlet of the nozzle of the sprayer 18 and theupper surface of the winglet wall 20 is about 7 cm.; the angle a betweenthe axis Y of the jet 18 and the plane X of the lower wing surface isbetween 60 and 75 degrees; and the angle b between the plane X and thetangent T is between 15 and 30 degrees.

Referring now to FIGS. 7 and 8, there is shown the airplane 10 fittedout with the conventional spraying equipment modified in accordance withthe teachings of the present invention, namely the addition of winglet16 (only one being shown), and the resulting downwardly directed vapourtrail in its wake.

As still more vividly shown in FIG. 9, the formation of thedroplet-transporting air-stream extending from the trailing edge of thewinglet 16--and hence the vapour trail of the droplets--comprises arelatively minor laminar flow LF over the middle portion, and swirling,vortical flows VF1 and VF2 along the two sides thereof. As can beclearly seen, the vortical air-streams have increasing radii as thedroplets approach the ground, thereby enabling the droplets to penetratethe foliage canopy to a far greater degree to ultimately rest at theirdesignated destination on the ground close to the crop stems. Moreover,a certain portion of the spiraling droplets reach from below to settleon the face-down sides of the leaves.

It will thus be recognised that by attaching simple,inexpensive-to-produce, winglets--which, in effect, in their simplestform are profiled, metal flaps--to existing spraying equipment,considerable savings of costly chemical preparation (and even flyingtime) is achieved, besides--and more importantly--the crops being moreeffectively treated by the chemical preparation.

It should be noted that the additional frictional resistance or draggenerated by the winglets is so insignificant so as to have a negligibleeffect on the flying characteristics of the airplane.

Although the invention has been described with reference to cropspraying, it will be readily understood that it can be applied to otheruses in aviational spraying, e.g. to cross-pollinization of fruit trees,where pollinization is usually not perfected by natural means (e.g. inAvocado plantations).

Those skilled in the art will readily appreciate the many changes,modifications and variations may be applied to the invention as so fardescribed without departing from the scope of the invention as definedin and by the appended claims.

What is claimed is:
 1. A method of spraying of crops by airplanes withspray jets provided behind and below the airplane wings, comprising thesteps of directing the spray jets downwardly at an acute angle withrespect to the lower wing plane, against a winglet comprising a convexdeflection surface, extending at a level distanced from the jet andtilted by an acute tangential angle with respect to the said wing plane.2. A method as claimed in claim 1 wherein the spray jets angle isbetween 60-75 degrees, the deflection surface having a radius ofcurvature of between 20-40 cm., and the tangential angle is between15-30 degrees.
 3. A method as claimed in claim 2 wherein the width ofthe deflection surface is between 30-100 cm., a plurality of suchsurfaces being provided underneath a series of aligned spray jets.
 4. Amethod as claimed in claim 3 wherein the deflection surface constitutesthe top wall of a convergent tunnel comprising a bottom wall conformingthe shape of and extending distantly from the top wall, and twoopposite, planar side walls, so that rectangular inlet and outletopenings are defined.
 5. A method of spraying of crops by airplaneshaving a series of aligned spray jets provided behind and below theairplane wings, comprising the steps of directing the spray jets at anacute angle of between 60-75 degrees with respect to the lower wingplane, against a plurality of winglets provided underneath said a seriesof aligned spray jets, each of said winglets comprising a convexdeflection surface having a radius of curvature of between 20-40 cm., awidth of between 30-100 cm. and extending at a level distanced from thejet and tilted by an acute tangential angle of between 15-30 degreeswith respect to the said wing plane, the deflection surface constitutingthe top wall of a convergent tunnel comprising a bottom wall conformingto the shape of and extending distantly from the top wall, and twoopposite, planar side walls, so that retangular inlet and outletopenings are defined, the radius of curvature of the bottom wall beingabout 10% less than that of the top wall.
 6. A method as claimed inclaim 5 wherein the cross-sectional area of the inlet opening is abouttwice that of the outlet opening.
 7. An airplane provided with sprayingequipment including a spray boom and a plurality of spray jets, thespray jets being positioned behind and below the airplane's wings andbeing directed downwardly at an acute angle with respect to the lowerwing plane against respective winglets each comprising a convexdeflection surface extending at a level distanced from the jet andtilted by an acute tangential angle with respect to the said wing plane.8. An airplane as claimed in claim 7 wherein the spray jet angle isbetween 60-75 degrees, the deflection surface having a radius ofcurvature of between 20-40 cm., and the tangential angle of between15-30 degrees.
 9. An airplane as claimed in claim 7 wherein the width ofthe deflection surface is between 30-100 cm., a plurality of suchsurfaces being provided underneath a series of aligned spray jets. 10.An airplane provided with spraying equipment including a spray boom anda plurality of aligned spray jets, the spray jets being directed at anacute angle of between 60-75 degrees with respect to the lower wingplane against a plurality of respective winglets provided underneathsaid aligned spray jets, each of said winglets comprising a convexdeflection surface having a radius of curvature of between 20-40 cm., awidth of between 30-100 cm. and extending at a level distanced from thejet and tilted by an acute angle of between 15-30 degrees with respectto the said wing plane, the deflection surface constituting the top wallof a convergent tunnel comprising a bottom wall conforming to the shapeof and extending distantly from the top wall, and two opposite, planarside walls, so that rectangular inlet and outlet openings are defined.11. An airplane as claimed in claim 10 wherein the radius of curvatureof the bottom wall is about 10% less than that of the top wall.
 12. Anairplane as claimed in claim 11 wherein the cross-sectional area of theinlet opening is about twice that of the outlet opening.